1. Field of the Invention
The present invention relates to a display device, and more particularly to a decoder circuit used in a drive circuit for driving a display panel.
2. Description of the Related Art
As a display device of an information communication terminal such as a computer or a television receiver set, a liquid crystal display device has been popularly used. An organic EL (Electroluminescence) display device (OLED: Organic light-Emitting Diode), a field emission display device (FED) or the like has been also known as a planar display device. The liquid crystal display device includes a liquid crystal display panel in which liquid crystal composition is sealed in a space formed between two substrates. By changing an electric field applied to the liquid crystal composition thus changing the alignment of the liquid crystal composition, a rate at which light passes through the liquid crystal display panel is changed so that an image is displayed. A display device including such a liquid crystal display device is provided with a drive circuit which supplies tone voltages. A decoder circuit which selects voltages corresponding to tone data is mounted in the drive circuit. Recently, there is observed tendency that the decoder circuit becomes large-scaled along with a demand for the enhancement of multi-tone leading to the increase of an area which the decoder circuit occupies in a semiconductor chip. In view of the above, the reduction of a scale of the decoder circuit is demanded.
JP 2001-34234 A discloses a two-input amplifier having two inputs. In this two-input amplifier, when two inputted voltages are equal, the inputted voltages are outputted, while when two inputted voltages differ from each other, an intermediate voltage between two voltages is outputted. JP 2001-34234 A discloses a technique which reduces the number of tone lines and a scale of a decoder circuit using the two-input amplifier.